Sunitinib: the first to arrive at first-line metastatic renal cell carcinoma

Tyrosine kinase inhibitors (TKIs) are beneficial for the treatment of renal cell carcinoma (RCC), gastrointestinal stromal tumors (GIST), pancreatic neuroendocrine tumors (pNETs), and other tumors. The antitumor activity of sunitinib has been based on time-related parameters such as progression-free survival (PFS) and overall survival (OS). Advances in knowledge of the molecular mechanisms and oncogenic processes associated with RCC have enabled the availability of rational targets for pharmacotherapy. Although each small molecule is modeled to block the activity of selected kinase signaling enzymes, it is increasingly evident that many have nontargeted effects (on other kinases) that may cause unexpected complications. The recommended dose for sunitinib in patients with advanced RCC is a 50 mg oral daily dose, with or without food, on a 4/2 week schedule (4 weeks "on" vs. 2 weeks "off") until progression. An alternative continuous 37.5 mg/day dosing schedule has also been evaluated and appears to be well tolerated, allowing the maintenance of the dose density of sunitinib with a similar outcome. The continuous administration schedule provides a constant exposure to the drug, and may prevent potential tumor regrowth and angiogenesis recovery. Most side effects are reversible and should not result in sunitinib discontinuation. In this article, the body of evidence behind the use of sunitinib in metastatic RCC (mRCC) compared to other targeted agents that have recently come into the field is summarized, and the need for correct management of an adverse event profile in order to better optimize available treatment options is underlined.